Regulation of Arabidopsis Early Anther Development by the Mitogen-Activated Protein Kinases, MPK3 and MPK6, and the ERECTA and Related Receptor-Like Kinases

Abstract

Mitogen-activated protein kinase (MAPK) and leucine-rich repeat receptor-like kinase (LRR-RLK) signaling pathways have been shown to regulate diverse aspects of plant growth and development. In Arabidopsis, proper anther development relies on intercellular communication to coordinate cell proliferation and differentiation. Two closely related genes encoding MAPKs, MPK3 and MPK6, function redundantly in regulating stomatal patterning. Although the mpk6 mutant has reduced fertility, the function of MPK3 and MPK6 in anther development has not been characterized. Similarly, the ERECTA (ER), ERECTA-LIKE1 (ERL1) and ERL2 genes encoding LRR-RLKs function together to direct stomatal cell fate specification and the er-105 erl1-2 erl2-1 triple mutant is sterile. Because the mpk3 mpk6 double null mutant is embryo lethal, anther development was characterized in the viable mpk3/+ mpk6/- and er-105 erl1-2 erl2-1 mutants. We found that both mutant anthers usually fail to form one or more of the four anther lobes, with the er-105 erl1-2 erl2-1 triple mutant exhibiting more severe phenotypes than those of the mpk3/+ mpk6/- mutant. The somatic cell layers of the differentiated mutant lobes appeared larger and more disorganized than that of wild-type. In addition, the er-105 erl1-2 erl2-1 triple mutant has a reduced number of stamens, the majority of which possess completely undifferentiated or under-differentiated anthers. Furthermore, sometimes, the mpk3/+ mpk6/- mutant anthers do not dehisce, and the er-105 erl1-2 erl2-1 anthers were not observed to dehisce. Therefore, our results indicate that both ER/ERL1/ERL2 and MPK3/MPK6 play important roles in normal anther lobe formation and anther cell differentiation. The close functional relationship between these genes in other developmental processes and the similarities in anther developmental phenotypes of the two types of mutants reported here further suggest the possibility that these genes might also function in the same pathway to regulate anther cell division and differentiation.

Molecular Profiling of Stomatal Meristemoids Reveals New Component of Asymmetric Cell Division and Commonalities among Stem Cell Populations inArabidopsis

“…Among all arrays, ERL1 (At5g62230) shows eightfold to 22-fold upregulation and ERL2 (At5g07180) a sevenfold to 35-fold increase. The finding underscores the known roles of the ERECTA family in promoting cell proliferation during shoot and flower development as well as restricting stomatal differentiation (Torii et al, 1996;Shpak et al, 2004Shpak et al, , 2005Pillitteri et al, 2007b;Hord et al, 2008). The LRR-RLK gene EMS1 was also transcriptionally enriched in scrm-D mute, WUS pro , and FIL pro (19-, 14-, and 24-fold, respectively).…”

ERECTA Family Genes Regulate Auxin Transport in the Shoot Apical Meristem and Forming Leaf Primordia

“…In addition to their function in the phloem and epidermis, ERf receptors promote integument growth (Pillitteri et al, 2007), regulate anther differentiation (Hord et al, 2008), and promote adaxial leaf identity (Xu et al, 2003). Here, we investigated the role of ERf genes in the vegetative SAM during leaf initiation.…”

Out of the Mouths of Plants: The Molecular Basis of the Evolution and Diversity of Stomatal Development

“…additional roles in various developmental processes in Arabidopsis (Shpak et al, 2004;Pillitteri et al, 2007a;Hord et al, 2008;van Zanten et al, 2009van Zanten et al, , 2010. Thus, TMM may be necessary for recognition of ligands or receptor complex activation specific to the stomatal lineage in all land plants.…”